support karmadactl config get-contexts

[zhzhuang-zju]

What type of PR is this?
/kind feature

What this PR does / why we need it:
support karmadactl config get-contexts to retrieve one or more contexts from a kubeconfig
Which issue(s) this PR fixes:
Parts of #4297

Special notes for your reviewer:
NONE
Does this PR introduce a user-facing change?:

support karmadactl config get-contexts to retrieve one or more contexts from a kubeconfig

[zhzhuang-zju]

Verification report：

• when no contexts in a kubeconfig

➜  karmada git:(master) ✗ _output/bin/linux/amd64/karmadactl config get-contexts 
CURRENT   NAME   CLUSTER   AUTHINFO   NAMESPACE

• others

➜  karmada git:(master) ✗ _output/bin/linux/amd64/karmadactl config get-contexts              
CURRENT   NAME                CLUSTER             AUTHINFO            NAMESPACE
          karmada-apiserver   karmada-apiserver   karmada-apiserver   
*         karmada-host        kind-karmada-host   kind-karmada-host   
➜  karmada git:(master) ✗ _output/bin/linux/amd64/karmadactl config get-contexts --no-headers 
      karmada-apiserver   karmada-apiserver   karmada-apiserver   
*     karmada-host        kind-karmada-host   kind-karmada-host